H-1 T-1 AND T-2 MEASUREMENTS OF THE MR-IMAGING CONTRAST AGENTS GD-DTPA AND GD-DTPA BMA AT 1.5T

We report in vitro T-1 and T-2 relaxation studies for the open-chain c omplexes Gd-DTPA and Gd-DTPA BMA. Measurements were performed on phant oms containing aqueous and plasma solutions of different concentration s by MR imaging in a 1.5T superconducting whole-body scanner. Longitud inal relaxation times T-1 were evaluated from serial turbo-FLASH exper iments for concentrations less than 1 mM, whereas for larger concentra tions the values were obtained from a standard inversion recovery (IR) sequence. Transverse relaxation times T-2 were determined using multi -echo spin-echo MRI protocols. The T-1 and T-2 relaxivities of the non ionic Gd-DTPA BMA are similar to those of the Gd-DTPA. The temperature dependencies of the relaxivities were determined over a temperature i nterval ranging from 21 to 50 degrees C and were found to be slightly different for the two contrast agents. In the case of Gd-DTPA BMA a la rger deviation of the expected temperature behavior of the relaxivitie s was observed as compared with Gd-DTPA. Deviations from a strictly li near dependence of relaxation times on temperature were found at lower concentrations in aqueous solutions. In plasma solutions a high T-1/T -2 ratio was observed for low concentrations, which decreased monotoni cally with increasing concentrations.